Contributions of local and regional sources to PM2.5 and its health effects in north India

Abstract Air quality in India, especially in north India, is increasingly severe due to rapid growth of industrialization and urbanization in past decades. Very few studies were conducted in the recent past to quantify regional contributions to high pollutant concentrations for designing effective control strategies. In this paper, source-oriented versions of Community Multi-scale Air Quality (CMAQ) model were applied to quantify the contributions of nine source regions (Delhi, Haryana & Rajasthan, Uttar Pradesh & Uttarakhand, Himachal Pradesh & Punjab, Central India, West India, South India, East & Northeast India and Outside India) to fine particulate matter (PM2.5) and its components including primary PM (PPM) and secondary inorganic aerosol (SIA) i.e. sulfate, nitrate and ammonium ions, in Delhi and three surrounding cities, Chandigarh, Lucknow and Jaipur in 2015. PPM is dominated by local sources (>70%), with Delhi as the top contributor in Delhi contributing to a maximum of 90 μg/m3 in winter. Unlike PPM, SIA contributions from non-local sources are more significant. Delhi, Haryana & Rajasthan, Uttar Pradesh & Uttarakhand, and Himachal Pradesh & Punjab contribute to ∼4 μg/m3 SIA concentrations in North India. In Delhi, local sources contribute to over 70% of total PM2.5, but the non-local sources are still important (over 30%) especially in winter. Furthermore, local emissions contribute less in highly polluted days compared to less polluted days indicating the importance of regional transport on high pollution episodes in Delhi. Overall, while local sources contribute to 1.495 × 104 premature deaths in Delhi, non-local sources contribute to 0.483 × 104 premature deaths.